The present invention relates generally to seat restraint systems for vehicles and, more particularly, to a variable load limiting restraint retractor for a seat restraint system in a vehicle.
It is known to provide a seat restraint system such as a seat belt in a vehicle to restrain an occupant in a seat of the vehicle. In some vehicles, the seat restraint system may be a lap belt, a shoulder belt or both. Typically, the lap belt and shoulder belt are connected together at one end. The seat restraint system includes a latch plate at the connected end. The seat restraint system also includes a buckle connected at one end by webbing or the like to vehicle structure. The buckle receives the latch plate to be buckled together. When the buckle and latch plate are buckled together, the seat restraint system restrains movement of the occupant to help protect the occupant during a collision.
It is also known to provide a restraint retractor for the seat restraint system. Typically, the restraint retractor has a spool attached to belt webbing of the seat restraint system and is rotatably mounted to the restraint retractor by a shaft. The restraint retractor has a spiral spring on one end of the shaft to urge the spool in a direction for retracting the belt webbing when not in use. Also, the restraint retractor has a toothed locking sprocket on the other end of the shaft and a locking pawl to engage the sprocket to lock the shaft against rotation in the other direction to prevent belt webbing unwinding. The locking sprocket is typically slaved to an acceleration sprocket via a spring and an acceleration pawl is actuated by an acceleration sensing mechanism or sensor. The acceleration sensor includes a mass member or xe2x80x9cstanding manxe2x80x9d that may be spherically shaped or frusto-conical in shape to engage and actuate the acceleration pawl.
The restraint retractor includes a load limiter such as a torque rod providing single (constant) level load limiting. Load leveling means that the restraint retractor will allow controlled belt webbing unwinding or payout. Some attempts have been made to provide a dual load limiter through the use of a torque rod, which only has two settings. Therefore, it is desirable to provide a multiple level or variable load limiting restraint retractor for a seat restraint system in a vehicle. It is also desirable to provide a restraint retractor for a seat restraint system in a vehicle that uses a magnetorheological fluid to provide a variable load limiting effect and, in some cases, a primary locking mechanism for the restraint retractor. It is further desirable to provide a variable load limiting restraint retractor for a seat restraint system in a vehicle that has infinite settings and reduced cost.
It is, therefore, one object of the present invention to provide a variable load limiting restraint retractor for a seat restraint system in a vehicle.
It is another object of the present invention to provide a variable load limiting restraint retractor for a seat restraint system in a vehicle that uses a magnetorheological fluid.
To achieve the foregoing objects, the present invention is a variable load limiting restraint retractor for a seat restraint system including a housing for operative connection to vehicle structure. The variable load limiting restraint retractor also includes a take-up spool operatively connected to the housing and connected to a belt of a seat restraint system for winding and unwinding the belt. The variable load limiting restraint retractor includes a rotatable shaft operatively connected to the take-up spool and the housing, the take-up spool being mounted on the shaft. The variable load limiting restraint retractor further includes a load limiting assembly operatively connected to the shaft for variably limiting load on the belt when the seat restraint system is in a buckled position.
One advantage of the present invention is that a variable load limiting restraint retractor is provided for a seat restraint system in a vehicle. Another advantage of the present invention is that the variable load limiting restraint retractor uses a magnetorheological fluid to provide multiple or infinite levels of load limiting, which allows for tailoring the load limit or restraint for each occupant, occupant weight and vehicle speed. Yet another advantage of the present invention is that the variable load limiting restraint retractor may provide the primary locking means for a restraint retractor, thus eliminating mechanical components now used to sense and lock the restraint retractor. Still another advantage of the present invention is that the variable load limiting restraint retractor reduces cost by eliminating mechanical components used for the primary locking mechanism, and improve quality by noise reduction due to limited mechanical components.